Studies On Magnetic Flux Leakage Testing Technology Of Corrosion For Steel Structure Of Large Crane

Lifting machinery is a kind of mechanical and electrical products of special equipment,which is used to carry out the machinery and equipment for the lifting,transportation,loading and unloading,installation and personnel transportation.With the rapid development of society and increasing scale of the production of lifting machinery,its variety and quantity is increasing.Lifting machinery,which is widely used in factories,mines,port,station,construction sites,warehouses,hydropower station,and other fields,is playing an increasingly important role in the modern enterprise production.Due to the relatively high frequency use of large crane,full load probability increase,Working environment is poor,such as high temperature,high corrosion,moisture,dust,etc..Lifting machinery safety has become one of the facing major problems in our country,In the event of accident,the economic will loss and cause the bad social influence.But for the present situation of detection of corrosion for steel structure of large crane,it is lack of a fast,reliable and high degree of automation of nondestructive testing method.Therefore,this thesis is combined with the National major scientific instrument and equipment development program" Development and application of high end electromagnetic detection instrument based on frequency domain variable "(NO.2012YQ090175)and the internal scientific research program of China special equipment inspection and Research Institute"Studies on magnetic flux leakage testing technology of corrosion for steel structure of large crane",(NO.2015.15)The Study on magnetic flux leakage testing technology of corrosion for steel structure of large crane is carried out mainly through laboratory experiments and field testing.The characteristics of typical signal of magnetic flux leakage detection are acquired,and the characteristics of magnetic flux leakage detection signal and feature extraction are studied,At the same time,the development of the automatic creeping magnetic flux leakage testing instrument are involved,which is suitable for the detection of corrosion for steel structure of large crane.The main work and achievements have completed as follows:(1)Assembly and debugging the automatic creeping leakage magnetic inspection instrument and its calibration method are studiedthe mechanical structure,the control unit,drive unit and the signal processing unit of the instrument assembly and welding are completed,test the performance and stability of the instrument,to verify the channel has good consistency and stability,Through the Sensitivity testing of the detection channel,the sensitivity was 800 as the setting parameters of the late stage,the thickness of the adjusting plate is 5mm.(2)The influence factors of magnetic flux leakage detection signal for large crane and frequency domain analysis are researchedAccording to the characteristics of the large crane steel structure,design and manufacture the plate with a transverse plate by continuous and intermittent welding,and design and manufacture more groups with different artificial defects and thickness of the experimental plates used for instrument calibration,and simulates site conditions of the steel structure surface with welding splash,oxide attached to the the surface of the corrosion parts.Magnetic flux leakage testing experiments of experimental was carried out,Study on the influence factors of magnetic flux leakage testing:the thickness of the plates and the location of defect,The types of defect,probe lift-off values,welding splash,oxide attached to the corrosion parts,Steel structure with support plate,and the frequency domain analysis of the magnetic flux leakage signal is carried out.Preliminary results are obtained.(3)The result of field magnetic flux leakage testing of large crane is analysisedThe results of the analysis of the magnetic flux leakage signals of the main girder with steel structure of large crane in a crane manufacturers are consistent with preliminary results in the laboratory,the magnetic flux leakage testing technology is applicable to detection of corrosion for steel structure of large crane is confirmed,and can carries on the preliminary quantitative analysis of the corrosion defects.